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UNT-SVX041D-EN
Installation - Piping
Coil Identification
Standard coil has the hot-water coil located in the reheat
position. Because the circuiting varies by the specific coil
design, the location of the inlet and outlet connections
may vary up and down. However, use the following rule to
be correct: The inlet is always the farthest away from the
entering-air-side; the outlet connection is always closest to
the entering-air-side.
Piping Arrangements for Chilled
and Hot-Water Coils
Two-Pipe Coils
Two-pipe coils have one inlet and outlet. Vertical high rise
fan coil units may have three to four rows on each unit. The
coil may be 100 percent chilled water, 100 percent hot
water, or with the addition of a pipe sensor for changeover
control, it may use chilled water when the chiller is
operating, or hot water when the boiler is operating. A
two-pipe system allows for the chiller or boiler to operate
independently, one at a time.
The pipe sensor must be clamped onto the supply water
line as close to the incoming water source as possible. Pipe
sensors are factory installed, but should be checked at the
time of installation for proper mounting. The pipe sensor
ensures that the thermostat operates in a mode
compatible with the water temperature in the coil.
All coils are piped so that the inlet is always on the row
farthest downstream from the incoming air as shown in
the following diagram.
Four-Pipe Coils
Four-pipe coils have a dedicated, chilled-water coil, and a
dedicated hot-water coil; each with its own inlet and outlet,
equaling four pipes. Trane coils use a common tube sheet
for four-pipe coils. Example: A four-row, chilled-water coil
and a one-row, hot-water coil would use a five-row coil
with four rows for chilled-water and one row for hot-water.
The one- or two-row hot-water coil is in the reheat
position. The controls are wired so that either the chilled-
water coil is operating or the hot-water coil is operating,
but not both at the same time (when typical fan coil
thermostats are used). When the conditioned space
thermostat is satisfied, both the chilled- and hot-water
control valves are closed. The same rule applies for inlet
and outlet locations as explained in the previous “Two-
Pipe Coils” section. Each chilled- and hot-water coil is
controlled individually so a pipe sensor is not required.
Figure 14.
Two-pipe coil arrangement
Note:
Actual configuration may vary.
Outlet
Airflow
Inlet
Figure 15.
Four-pipe coil arrangement
Note:
Actual configuration may vary.
Outlet
Airflow
Inlet
Outlet
Inlet
